QwtWidgetOverlay - An overlay for a widget.

       Generated automatically by Doxygen for Qwt User's Guide from the source code.

Version 6.1.4                                    Wed Jan 2 2019                              QwtWidgetOverlay(3)

QwtWidgetOverlay::QwtWidgetOverlay(QWidget*widget)
       Constructor.

       Parameters:widget Parent widget, where the overlay is aligned to

       An overlay for a widget.

       The main use case of an widget overlay is to avoid heavy repaint operation of the widget below.

       F.e. in combination with the plot canvas an overlay avoid replots as the content of the canvas can be
       restored from its backing store.

       QwtWidgetOverlay is an abstract base class. Deriving classes are supposed to reimplement the following
       methods:

       • drawOverlay()

       • maskHint()

       Internally QwtPlotPicker uses overlays for displaying the rubber band and the tracker text.

       Seealso:QwtPlotCanvas::BackingStore

enumQwtWidgetOverlay::MaskMode
       Mask  mode.  When  using  masks  the widget below gets paint events for the masked regions of the overlay
       only. Otherwise Qt triggers full repaints. On less powerful hardware ( f.e embedded systems ) -  or  when
       using the raster paint engine on a remote desktop - bit blitting is a noticeable operation, that needs to
       be avoided.

       If  and  how  to  mask depends on how expensive the calculation of the mask is and how many pixels can be
       excluded by the mask.

       The default setting is MaskHint.

       Seealso:setMaskMode(), maskMode()EnumeratorNoMask Don't use a mask.

       MaskHint
              Use maskHint() as mask. For many situations a fast approximation is good  enough  and  it  is  not
              necessary to build a more detailed mask ( f.e the bounding rectangle of a text ).

       AlphaMask
              Calculate  a  mask  by  checking  the  alpha  values.  Sometimes it is not possible to give a fast
              approximation and the mask needs to be calculated by drawing the overlay and testing the result.

       When a valid maskHint() is available only pixels inside this approximation are checked.

   enumQwtWidgetOverlay::RenderMode
       Render mode. For calculating the alpha mask the overlay has already been painted to a  temporary  QImage.
       Instead of rendering the overlay twice this buffer can be copied for drawing the overlay.

       On  graphic  systems  using the raster paint engine ( QWS, Windows ) it means usually copying some memory
       only. On X11 it results in an expensive operation building a pixmap and for simple overlays it might  not
       be recommended.

       Note:
           The render mode has no effect, when maskMode() != AlphaMask.

       EnumeratorAutoRenderMode
              Copy the buffer, when using the raster paint engine.

       CopyAlphaMask
              Always copy the buffer.

       DrawOverlay
              Never copy the buffer.

virtualvoidQwtWidgetOverlay::drawOverlay(QPainter*painter)const[protected],[purevirtual]
       Draw the widget overlay

       Parameters:painter Painter

   boolQwtWidgetOverlay::eventFilter(QObject*object,QEvent*event)[virtual]
       Event filter. Resize the overlay according to the size of the parent widget.

       Parameters:object Object to be filtered
           event Event

       Returns:
           See QObject::eventFilter()

   QRegionQwtWidgetOverlay::maskHint()const[protected],[virtual]
       Calculate an approximation for the mask.

       • MaskHint The hint is used as mask.

       • AlphaMask The hint is used to speed up the algorithm for calculating a mask from non transparent pixels

       • NoMask The hint is unused.

       The default implementation returns an invalid region indicating no hint.

       Returns:
           Hint for the mask

   QwtWidgetOverlay::MaskModeQwtWidgetOverlay::maskMode()constReturns:
           Mode how to find the mask for the overlay

       Seealso:setMaskMode()voidQwtWidgetOverlay::paintEvent(QPaintEvent*event)[protected],[virtual]
       Paint event

       Parameters:event Paint event

       Seealso:drawOverlay()QwtWidgetOverlay::RenderModeQwtWidgetOverlay::renderMode()constReturns:
           Render mode

       Seealso:RenderMode, setRenderMode()voidQwtWidgetOverlay::resizeEvent(QResizeEvent*event)[protected],[virtual]
       Resize event

       Parameters:event Resize event

   voidQwtWidgetOverlay::setMaskMode(MaskModemode)
       Specify how to find the mask for the overlay.

       Parameters:mode New mode

       Seealso:maskMode()voidQwtWidgetOverlay::setRenderMode(RenderModemode)
       Set the render mode

       Parameters:mode Render mode

       Seealso:RenderMode, renderMode()voidQwtWidgetOverlay::updateOverlay()
       Recalculate the mask and repaint the overlay

       QwtWidgetOverlay - An overlay for a widget.

       #include <qwt_widget_overlay.h>

       Inherits QWidget.

       Inherited by QwtPickerRubberband, and QwtPickerTracker.

   PublicTypes
       enum MaskMode { NoMask, MaskHint, AlphaMask }
           Mask mode.
       enum RenderMode { AutoRenderMode, CopyAlphaMask, DrawOverlay }
           Render mode.

   PublicMemberFunctionsQwtWidgetOverlay (QWidget *)
           Constructor.
       virtual ~QwtWidgetOverlay ()
           Destructor.
       void setMaskMode (MaskMode)
           Specify how to find the mask for the overlay.
       MaskModemaskMode () const
       void setRenderMode (RenderMode)
       RenderModerenderMode () const
       void updateOverlay ()
       virtual bool eventFilter (QObject *, QEvent *)
           Event filter.

   ProtectedMemberFunctions
       virtual void paintEvent (QPaintEvent *event)
       virtual void resizeEvent (QResizeEvent *event)
       virtual QRegion maskHint () const
           Calculate an approximation for the mask.
       virtual void drawOverlay (QPainter *painter) const =0